Extreme clownfish pairing aggression

TSM Aquatics


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Feb 17, 2021
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I bought two juvenile black ice clownfish (both ~1 inch) three weeks ago. Things were going smoothly up until a week and a half ago when the smaller of the two clownfish started acting aggressive to the other clownfish, which I attributed to normal pairing behavior.

However, the aggression has become extreme as of last week and the smaller clownfish will chase and nip the larger clownfish causing fin damage and it'll relentlessly chase the larger clownfish from any hiding spot. The smaller, aggressive clownfish will quiver and shake however this behavior is not reciprocated by its partner. I've tried to isolate the aggressive clownfish in a breeder box twice, each for three days, however the attacks continue once I release it.

I'm to the point where I'm ready to bring in one of the clownfish to my LFS to exchange for another given the severity of the aggression and the fin damage. Should I try to wait it out for a little while or am I right to want to exchange the fish now? Also, given the odd behavior from the docile clownfish (unwilling to quiver/show submission), would it be best to exchange the aggressive or bullied clownfish for a new one since it's likely the replacement will need to pair with the remaining clownfish?


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Jun 6, 2008
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Some times clowns just don't get along. If you put a divider in your tank after a while. Only remove it if both clowns hang out together without signs of aggression.
Your LFS probably will not want to take the beaten up fish back. Which ever you take back try to get a smaller one if you do.
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